1. Field of the Invention
The invention relates to a process of chlorosulfonation of a class of poly(ether sulfones) which are known to be notoriously difficult to sulfonate. The novel chlorosulfonated poly(ether sulfones) and derivatives thereof are useful as membrane forming materials for a variety of separation processes, e.g. reverse osmosis, ultra-filtration, ion exchange, electrodialysis and like processes.
2. Brief Description of the Prior Art
Sulfonation of polysulfones is disclosed in U.S. Pat. No. 3,709,841, wherein Quentin describes a preparation of polyaryl polymers in which part of the aromatic rings are substituted with hydroxysulfonyl radical (--SO.sub.3 H) also called sulfonic acid groups. However, aromatic poly(ether sulfones) such as those made up of repeating units of the formula: ##STR2## wherein Ar.sub.1 and Ar.sub.2 (which may be the same or different) are phenylene, or partially substituted phenylene with non-deactivating groups; and L represents a divalent linking group such as such as oxygen, are notoriously difficult to sulfonate on the aromatic rings in the chain due to the electron withdrawing effect of the sulfone linkages which deactivate the adjacent aromatic rings for electrophilic substitution. Sulfonation of these polymers with chlorosulfonic acid or oleum at ambient temperatures require an enormous excess of sulfonation agent and results in a highly degraded product with extents of sulfonation that are impossible to control. The surplus of sulfonation agent complicates the workup procedures (see U.S. Pat. No. 4,272,903, Examples 11 and 12). In order to overcome the above difficulties, copolymers of the above polysulfones have been prepared that contained in addition to the repeat unit (I) described above, a variable amount of easily sulfonatable units of the formula: ##STR3## (see the above cited U.S. Pat. No. 4,273,903).